Retrievable bridging plug for sealing a well casing bore



RETRI SEALING A WELL CASING BORE 5 Sheets-Sheet 1 Filed Jan. 5, 1965 R m5 m N R a, m M m m 5 Z A w j 0 J 9 a r @f 1 2 2 R 9 a f}... V z 5 a v @w9 5 N w 1%, ,W 9 @3 2% 6 7 E w a 3 AM 7 l H "NH n c M 7 i 2 .7 N, 0 g J4k m 6 u. 5 I w a m a 5 g 3 7 I 9 A, /4/ 34m. 3 5 3 6 9 7 5 w /3 .4, M g2 2 Z June 13, W7 MCHEZNRY DAVIS 3,324,949

RETRIEVABLE BRIDGING PLUG FOR SEALING A WELL CASING BORE 5 Sheets-Sheet2 Filed Jan. 6, 1965 June 13, E97 M HENRY DAVIS RETRIEVABLE BRIDGINGPLUG FOR SEALING A WELL CASING BORE 5 Sheets-Sheet 5 Filed Jan 5, 1965NVENTOR I'Wa l fe/aw). A V I5 June 13, 1967 M HENRY mvls 393249949RETRIEVABLE BRIDGING PLUG FOR SEALING A WELL CASING BORE Filed Jan. 5,1965 5 Sheets-Sheet 4 1N VENTOR MCHkiA/RY DAV/5 ATTORNEY 5 Sheets-Sheet5 My 6 w. E W m A 6 a a 4 0% 9 y 5 m 3+ June 13, 1&7.

E BRIDGING PLUG FOR SEALING A WELL CASING BOR Filed Jan. 5, 1965 UnitedStates Patent 3,324,949 RETRIEVABLE BRIDGING PLUG FUR SEALING A WELLCASING BGRE McHenry Davis, San Marcos, Tern, assignor of one-half toOllie P. Davis and Tommy G. Davis, jointly, both of Houston, Tex.

Filed Jan. 5, 1965, Ser. No. 423,504 Claims. (Cl. 166-63) ABSTRACT OFTHE DISCLGSURE tain of the illustrated parts in different positions fromthe positions of said parts in FIGURES 2B and 2C;

FIGURE 4 is an enlarged detail sectional view of a part of the structureas seen in FIGURE 23;

FIGURE 5 is an enlarged cross sectional view of the retrievable plugtaken substantially along a plane as indi cated by the line 55 of FIGURE2C;

FIGURE 6 is a fragmentary longitudinal sectional view of a part of theretrievable plug taken substantially along the line 66 of FIGURE 5FIGURE 7 is a cross sectional view of a part of the plug takensubstantially along a plane as indicated by the latches itself to theplug so that the plug is retrieved with the retrieving unit.

This invention relates to a bridging plug capable of being lowered to adesired position in the bore of a well casing, and to be expanded whileso located for clamping the plug to the casing wall for sealing the boreof the casing.

Another object of the invention is to provide a retrievable plugincluding a lowering unit by which the plug is supported while beinglowered to a desired location in the casing bore and which includesmeans to effect expansion of the plug after it has been lowered to adesired depth for sealing the casing bore, and for unlatching thelowering unit from the plug so that said unit can be retrieved from theplug while the plug remains clamped to the well casing.

A further object of the invention is to provide a retrieving unit whichmay be subsequently lowered into line 77 of FIGURE 4 and on a greatlyenlarged scale;

FIGURE 8 is an enlarged cross sectional view through a part of the plug,taken substantially along a plane as indicated by line 8-8 of FIGURE 2C;

FIGURE 9 is an enlarged bottom plan view of certatin of the parts of theplug, shown detached therefrom;

FIGURE 10 is an enlarged cross sectional view illustzrating in detailcertain of the parts as seen in FIGURE FIGURE 11 is a view similar to aportion of FIGURE 3, on a slightly enlarged scale relative thereto, andshowing a part of the lowering unit replaced by parts to form theretrieving unit;

FIGURE 12 is an enlarged front elevational view, partly in section, of adouble check valve constituting a part the well casing and intoengagement with the bridging plug for releasing the plug for clampingengagement with 1 the Well casing and for latching the plug to saidretrieving unit whereby the plug can be recovered from the well casingwith the retrieving unit.

Still a further object of the invention is to provide valve meansforming a part of the retrievable plug to release the pressure ofhydrostatic well fluids and circulating fluids from a part of the plugto facilitate entrance of the retrieving unit into said part.

Various other objects and advantages of the invention will hereinafterbecome more fully apparent from the following description of thedrawings, illustrating a presently preferred embodiment thereof, andwherein:

FIGURE 1 is a fragmentary view primarily in side elevation and partiallyin longitudinal section showing the bridging plug in an applied positionin a well casing;

FIGURE 2A is an enlarged fragmentary longitudinal sectional view, partlyin elevation, of an upper part of the retrieving unit;

FIGURE 2B is an enlarged longitudinal, substantially central verticalsection view of the lower portion of the lowering unit and the upperportion of the retrievable bridging plug;

FIGURE 2C is a fragmentary longitudinal substan tially central verticalsectional view of the remaining,

lower portion of the plug;

FIGURE 3 is an enlarged longitudinal substantially central verticalsectional view, partly in elevation, showing a part of the structure asseen in FIGURE 2B and a part of the structure as seen in FIGURE 20, withcerof the retrievable plug;

FIGURE 13 is a longitudinal, substantially central sectional viewthereof, taken substantially along the line 13-13 of FIGURE 12;

FIG. 14 is a top plan view of the check valve on reduced scale;

FIGURE 15 is a cross sectional view of the check valve, takensubstantially along a plane as'indicated by the line 1515 of FIGURE 13,and on a reduced scale;

FIGURE 16 is a similar view taken substantially along a plane asindicated by the line 16-16 of FIGURE 13; and 4 FIGURE 17 is a similarview taken substantially along a plane as indicated by the line 1717 ofFIGURE 13.

Referring more specifically to the drawings, the retrievable plug in itsentirety and comprising the invention is designated generally 20 andincludes a bridging plug 21 and a lowering and anchoring unit 22. v

The bridging plug 21 includes a sleeve 23 constituting the lower endthereof, as best seen in FIGURES 1 and 2C, and which includes a topportion 24 and a bottom portion 25. An intermediate portion 26 extendsbetween the end portions 24 and 25 and is provided withcircumferentially spaced slots 27 which extend from end to end thereof.A clamping bar 28 is mounted in each slot 27. Each bar 28 has a set ofteeth 29 disposed crosswise of one end thereof and which face toward theother end of said bar. The clamping bars 28 are arranged so that theteeth 29 of adjacent bars are disposed at the opposite ends of theintermediate portion 26 and face in opposite directions. An elastic tube30, formed preferably of plastic or rubber, lines the interior of theintermediate portion 26 and is bonded thereto and to the inner surfacesof the clamping bars 28.

The bridging plug 21 includes a collar 31 which is disposed above andspaced from the sleeve 23. An elastic tube 32 has a lower portionextending through the sleeve 23 internally of the tube 30, and an upperend which is disposed in the collar 31. The bottom sleeve portion 25defines a downwardly opening cup in which a plug 33 is threadedlymounted, as seen at 34. The lower end of the tube 32 is clamped, as seenat 35 in FIGURE 2C, between parts of the bottom sleeve portion 25 andthe plug 33. A plug 36 is threaded downwardly, as seen at 37, into theupper portion of the collar 31, and the upper end of the tube 32 isclamped, as seen at 38, between opposed portions of the collar 31 andplug 36. A plurality of sealing rings 39 are mounted on the tube 32between the top sleeve portion 34 and the collar 31. The sealing rings39 are formed of plastic or rubber of substantial hardness but arecapable of being stretched. The upper portion of the top part 24 of thesleteve is internally recessed, as seen at 40, to receive a hard rubberor plastic abutment ring 41 and the lower end of the collar 31 isinternally recessed, as seen at 42, to accommodate a similar abutmentring 43. Sealing rings 39 are retained in spaced apart relation to oneanother and to the abutment rings 41 and 43 by resilient spacing rings44, each of which preferably comprises an annular coil spring 45 encasedin a rubber tube 46, as best seen in FIGURE The plug 30 has 21 dependingexternally threaded boss 47 and a central bore 48 which extends from topto bottom t-herethrough and through said boss. A cap 49 (FIG. URE 2C)threadedly engages the boss 47 to support a tube 50 the lower end ofwhich engages in the bore 48. The cap 49 has a depending internallythreaded hollow neck 51 which is normally closed and sealed by threadedplug 52. The upper end of the tube 50 seats in a downwardly openingcentrally disposed socket 53 of the plug 36. An elongated sealedcontainer 54, preferably of plastic or rubber, is disposed in andextends from end-to-end of the tube 50 and is filled with an expansiblegas, such as carbon dioxide or with compressed air.

The plug 36 has an upwardly extending internally threaded annular flange55 in which the externally threaded lower end 56 of a housing member 57threadedly engages. The housing 'member 57 is of circular cross section,as seen in FIGURE 8, and has a head 58 defining its upper end. As bestseen in FIGURE 3, the housing member 57 combines with the plug 36 toform a chamber 59. The head 58 has a downwardly opening frusto-conicalcavity 60 forming a downwardly opening valve seat, the upper end ofwhich communicates with a restricted central bore 61 of the head 58which opens upwardly thereof into an annular externally threaded flange62, constituting the upper end of the head 58. The plug 36 has a ring ofspaced openings 63 forming ports connecting the chamber 59 to theannular chamber 64 formed by the tube 32 and the plugs 33 and 36.

A tubular guide member 65 is disposed axially in the chamber 59 and hasits lower end threadedly engaging in a centrally disposed threadedopening 66 of the plug 36 which opens downwardly therethrough into thesocket 53, so that the lower end of the guide 65 abuts the upper end ofthe container 54. The guide 65 has a restricted bore portion 67 toslidably receive and guide a valve stem 68 which extends downwardly froma valve 69. The guide 65, between the bore portion 67 and the plug 36.has ports 70 opening outwardly of the lower portion of the bore thereofinto the chamber 59. The part of the bore of the guide 65, disposedabove the restricted bore portion 67, defines an upwardly opening socket71 in which the lower end of a compression spring 72 seats. The spring72 surrounds the upper portion of the valve stem 68 and has its upperend bearing against the under side of the valve 69.

The valve 69 is cone shaped and is normally held by the spring 72 seatedin the valve seat 60 for closing the upper end of the chamber 59. Asseen in FIGURE 2B, as thus disposed, the upper end of the valve 69extends through the opening 61. The valve 69 has an annular groove 73intermediate of its ends containing an O-ring 74 of rubber or othersuitable material, providing an effective seal between the valve 69 andthe valve seat 60 when the valve is in its closed position of FIGURE 2B.The diameter of the valve 69 at its lower large end is substantiallyequal to the diameter of the chamber 59 below the valve seat 60, so asto have a relatively close fitting engagement therewith. The bottomportion of the periphery of the valve 69 has notches 75 forming passagesbetween the lower portion of chamber 59 and the valve seat 60, when thevalve is in an open position. The valve stem 68 has a pointed lower end76 which is disposed in the guide 65, above and spaced from thecontainer 54, when the valve 69 is in a closed position, as seen inFIGURE 2C.

An upper housing member 77, of circular cross section, has a lower endwhich is internally enlarged and internally threaded, as seen at 78,which is connected to the flange 62, and a tapered upper end 79 forminga frustoconical flange which terminates a threaded opening 80. A tube 81has a lower end threadedly engaging in the opening for supporting saidtube above the housing 77. The housing 77 defines an upper chamber 82.

The plug 36 has an internally enlarged and internally threaded annulartop flange 82 which surrounds the lower portion of the annular flange 55to receive an externally restricted and externally threaded lower end 83of a large tube 84, which is thereby threadedly connected to the collar31. The tube 84 extends upwardly to beyond the upper end of the tube 81,as seen in FIGURE 2B, and is disposed around and spaced from thehousings 57 and 77. A plug 85 is secured in an upper end of the tube 84and has a central opening 86 in which the upper end of the tube 81 issecured. The top of the plug 85 and the upper end of the tube 81 aredished as seen at 87 to provide a guide for the lowering and anchoringunit 22, as will hereinafter be described. The tube 84 combines with theplugs 36 and 85 to form a relief chamber 88. A check valve 89 has a pipeextension 90 which threadedly engages at its lower end in a threadedopening 91 of the flange 79, for supporting the check valve on the upperhousing member 77 within the relief chamber 88, and in communicationwith the chamber 82. The check valve 89 will hereinafter be described.

The lowering and anchoring unit 22 includes a tubular sheath 92 composedof threadedly connected tubular sheath sections 93, 94, 95, 96, 97, anda head section 98 which is threadedly connected to the upper end of theupper tubular sheath section 93, as seen .in FIGURE 2A. An electric wire99 extends downwardly through a bore 100 of the head section 98, throughthe upper sheath section 93 and into the sheath section 94 disposeddirectly therebeneath. Wire 99 is connected to an explosive containingcartridge 101 which is contained in the sheath section 94. The conductorWire 99 is of a conventional type covered with electrical insulation.Wire 99 extends upwardly from the head 98 through a tubular metal casing102 which is secured at its lower end to the head 98 for supporting theunit 22 and the plug 21.

A piston 103 is slidably disposed in the sheath section 95, beneath andspaced from the explosive charge 101, and has a piston rod 104 extendingdownwardly therefrom and which is connected to the upper end of an upperplunger section 105 at its lower end. The plunger section 105 iscontained in the lower portion of the sheath section 96 which has arestricted bore portion 106 disposed above and spaced from said plungersection and forming a guide for the piston rod 104. The lower end of theplunger section 105 has a threaded socket 107 to receive a threadedprojection 108, constituting the upper end of a lower plunger section109 which is contained in the bottom-most sheath section 97. A shear pin110 extends through the plunger section 105 and the sheath section 96for holding the plunger 105, 109 positioned as seen in FIGURES 2B and 4.

The lowermost sheath section 97 has oppositely disposed slots 111 whichopen outwardly of the lower end thereof, each of which accommodates alatch member 112. The latch members 112 are pivotally mounted in theslots 111 on pivot pins 113 and each has a depending latch arm 114 whichterminates in an out-turned hookshaped terminal or finger 115. Thelatches 112 each have an upwardly extending longitudinally curved camarm 3,3 116, constituting the part thereof disposed above the pivot 113.

A latch retainer 117 is pivotally mounted in each slot 111 on a pivotpin 118, above the latch 112, and includes a depending cam arm 119, theterminal of which bears against the outer concave edge of the cam arm116 of the latch disposed therebeneath. Each latch retainer has a leafspring 120 rising from its pivot 118 and terminating in an out-turnedhook 121 which bears yieldably against the top wall 122 of the slot 111thereof.

As best seen in FIGURE 7, torsion springs 123 are wound on the pivotpins 113 and have their outer ends anchored in the sheath section 97 andtheir inner ends anchored in the latches 112. The springs 123 are woundin directions to urge the latch arms 112 to swing outwardly toward theirfull line positions of FIGURE 4. Torsion springs 124 are disposed on thepivot pins 113 with their inner ends anchored in the latch retainers 117and their outer ends anchored in the sheath section 97. The springs 124are wound in directions for urging the cam arms 119 to swing inwardlytoward their full line positions of FIGURE 4.

The plunger section 109 has opposed grooves 125 which are provided withconcave bed portions for accommodating the cam arms 116. To apply theretrievable plug 21 and before it is inserted in the upper end of thewell casing 126, the lowering and anchoring unit, assembled asheretofore described and as illustrated in FIGURES 2A and 2B, isinitially inserted through the tube 81. The latch fingers 115 willinitially engage the dished cam surface 87 and will be cammed inwardlythereby from their full line toward their dotted line positions ofFIGURE 4, so that the sheath section 97 can enter the tube 81 and movedownwardly therethrough to its position of FIG- URES 2B and 4. As thelatch fingers 115 clear the lower end of the tube 81, the latches 112will be urged to swing from their dotted line to their full linepositions of FIG URE 4 by the springs 123, to cause the fingers 115 toengage the inner surface of the flange 79 for latching the unit 22 tothe plug 21. As seen in FIGURE 4, the convex outer sides of the cam arms116 conformably engaged in portions of the beds of the grooves 125 whenthe latches 112 are in their full line latching positions. As thelatches 112 swing to their full line positions, the latch retainers 117are oscillated by the springs 124 for causing the cam arms 119 to swinginwardly to their full line positions of FIGURE 4 against the cam arms116, and for causing the leaf springs 120 to swing outwardly toward thewall of the tube 81. This outward movement of the springs 12% causes thesprings to be compressed endwise so that the hook portions 121 thereofare brought into tighter frictional engagement with the slot ends 122 toeffectively resist any tendency of the latches 112 to swing back towardtheir dotted line positions, which would necessitate forcing theretainers 117 to be swung back toward their dotted line positions inFIGURE 4. As seen in FIGURE 2B, sheath section 95 has O-rings 95 to sealthe tube 81 when the unit 22 is latched to plug 21.

The plug 21 as thus attached to the unit 22 is lowered into the casing126 to a desired location. A switch, not shown, located at the surfaceof the well, is then closed to complete a circuit through the wire 99 tothe explosive charge 101 which is grounded through the sheath 92 andmetal parts of the plug 21 to the casing 126 to effect detonation of thecharge. When this occurs, the explosive charge is channeled and shapedin its passage initially through the bore portion 127 and thence throughthe flared bore portion 128 (FIGURE 2B) to concentrate the force of thecharge against the upper end of the piston 103. The initial impact ofthe charge against the piston will drive the piston downwardly withsutficient force to sever the shear pin 110. The plunger 105, 109 willbe driven downwardly by the force of the explosion from its position inFIGURES 2B and 4 to its position of FIG- URE 3. During the initialdownward movement of the lower plunger section 109, the grooves will camthe arms 116 outwardly as the upper ends of said grooves move intocontact with said arms, for swinging the latches 112 and the latchretainers 117 back to their dotted line positions of FIGURE 4 and totheir positions of FIG- URE 3. The plunger section 109 continues to movedown wardly through the chamber 32 until the cavity 129 in the headthereof engages the upper end of the valve 69. The valve 69 is thendriven downwardly by the plunger section 109 as the lower end thereofmoves through the opening 61 and to substantially the position of FIGURE3. This drives the valve stem 68 downwardly through the guide 65 tocause the pointed end 76 thereof to pierce the upper end of thecontainer 54. The downward movement of the valve 65 compresses thespring 72 which reacts after the valve 69 has reached its position ofFIGURE 3 to return the valve to its raised position of FIGURE 2B forclosing the valve seat 69 and for retracting the stem 68 out ofengagement with the container 54 and back to its position of FIGURE 20.The compressed air or carbon dioxide gas then escapes through thepierced upper end of the container 54 into the chamber 59, through theports '70 and back into the chamber 64 through the ports 63, forexpanding the tubes 32 and 30. Expansion of the upper portion of thetube 32 stretches and enlarges the sealing rings 39 for bringing saidrings into tight sealing engagement with the wall of the casing 126 forsealing off the casing bore 130 above and below the sealing rings 39.Expansion of the lower part of the tube 32 distends parts of the tube 30which are in registration with the slots 27 and attached to the clamps28, for forcing the clamps outwardly through the slots 27 to cause theteeth 29 thereof to bite into the casing 126 for effectively retainingthe plug against movement lengthwise of the casing. It will be apparentthat the upwardly inclined teeth 29 at the lower end of the clamps willeffectively resist upward movement of the plug 21, while the downwardlyinclined teeth 29 at the upper ends of the clamps 28 will effectivelyprevent downward displacement of the plug.

Since the plunger section 109 will only be retracted sufiiciently by thespring 72 to permit the valve 69 to resume its closed position toprevent escape of any of the compressed medium from the container 54through the valve seat 64 said plunger section 109 will not return toits position of FIGURE 4 so that the latches 112 and latch retainers 117will be retained in their positions of FIGURE 3. Accordingly, when anupward pull is exerted on the cable 102, unit 22 will be extracted fromthe tube 81 and can be recovered.

The nipple 1118 is then unscrewed from the socket 107 to detach thebottom plunger section 1619; and the bottom sheath section 97 isunscrewed from the sheath section 96. The upper plunger section 1115 isthen returned to its position of FIGURE 2B and a new shear pin 110 isapplied for securing the plunger section 195 to the sheath section 96.

An elongated hammer 131 is then applied to replace the plunger section169 and the sheath section 97 to convert the lowering and anchoring unit22 unto the retrieving unit 132 which otherwise corresponds to saidlowering unit 22. The hammer 131 has an outer diameter correspondingwith the outer diameter of the sheath section 97 and has an internallythreaded socket 133 at its upper end in which the threaded nipple 134 atthe lower end of the sheath section 96 threadedly engages. A smallthreaded stem 135 extends upwardly from the bed of the socket 133 andthreadedly engages in the threaded socket 197 for threadedly connectingthe hammer 131 to the sheath section 96 and the plunger section 165.

The hammer 131 has oppositely disposed outwardly opening grooves 136 and137 containing latching fingers 13S and 139, respectively, which arepivotally mounted in the lower ends of said grooves by pivot pins 140and 141, respectively. The hammer 131 has transversely disposed sockets142 and 143 which open into the grooves 136 and 137, respectively, andwhich contain compression springs 144 and 145, respectively. The hammer131 has a tapered frusto-conical lower end 14 which has a cavity 147 inthe end thereof; and an O-ring 148 is disposed in a groove 149 of thehammer which is disposed above and adjacent its end portion 146.

As seen in FIGURE 2B, 21 housing 150 is secured to the exterior of thetube 81 and is disposed within the chamber 88. The housing 150 has aninternally restricted lower portion 151 containing a sliding gate valve152 having a port 153 which registers with aligned ports 154 and 155 ofthe tube 81 and housing 150, respectively, in the open position of saidvalve 152, as seen in FIG- URE 2B. A valve stem 156 extends upwardlyfrom the valve 152 through guides 157 and 158 which are attached to theexterior of the tube 81 and disposed in the housing 150. A lever 159 isslidably and pivotally mounted on a pin 160 which spans a slot 161 ofthe tube 81. The pin 160 engages a slot 162 of said lever. The upper endof the rod 156 is pivoted at 163 to the lever 159. A pull spring 164 isattached at its upper end to the rod 156 and at its lower end to theguide 158 for urging said rod downwardly to move the valve 152downwardly to a closed position. An O-ring 165 forms a seal around theinner end of the port 155.

When the lowering and anchoring unit 22 is applied to the plug 21, aspreviously described, it will move the valve 152 to its open position;however, the valve 152 functions only with the retrieving unit 132 andwill be returned by the spring 164 to a closed position, as seen indotted lines of FIGURE 2B, when the lowering and anchoring unit 22 isrecovered from the plug 21.

To retrieve the plug 21, the retrieving unit 132 is lowered into thecasing 126 and its leading end 146 will engage the surface 87 and beguided thereby into the tube 81. The O-ring 148 upon entering the tube81 will seal the upper end of said tube and the inner end of the lever159 will be engaged by the tapered portion 146 and will be swungcounterclockwise and also caused to slide on the pin 160 from its dottedline to its full line position of FIGURE 2B, to thereby raise the valve152 to its open position so that hydrostatic fluids and circulatingfluids which have filled said tube and the chamber 82 will escapethrough the aligned ports 153, 154 and 155 into the relief chamber 88.

As the hammer 131 moves downwardly into the tube 81 the latch fingers138 and 139 will be swung inwardly into the grooves 136 and 137,respectively, to allow the latch fingers to move downward with thehammer 131 through the tube 81. A sufficient amount of the fluidcontained in said tube 81 and the chamber 82 will escape tosubstantially reduce the pressure in the chamber 82 before the ring 148passes the port 154 to shut off further escape of the fluid outwardlytherethrough. The fluid then remaining in the chamber 82 will be at asufficiently low pressure to enable it to escape through the valve 89,as it will hereinafter be described in detail.

The hammer 131 will pass downwardly through the chamber 82 and thecavity 147 thereof will strike the top of the valve 69 with suflicientforce to force the valve downwardly to its open position of FIGURE 11.In this position of the hammer 131, the latch fingers 138 and 139 willhave cleared the lower end of the tube 81 so that the spring 144 and 145thereof, respectively, may swing said latch fingers outwardly to theirlatched positions, as illustrated. As thus disposed, the valve 69 willbe held open by the hammer 131 and the tapered portion 146 thereof willclose the passage 61. However, the head 58 has radial passages 166opening outwardly into the relief chamber 88 and communicating with thevalve seat 60, so that the compressed gas or air in the chambers 59 and64 can escape past the notches 75 and between the valve 69 and seat 60to the passages 166 from which the gas can escape to the relief chamber88. As the pressure diminishes in the chamber 64, clamps 28 will bedrawn inwardly and back to their positions of FIGURE 2C by the elastictube 30, and the sealing rings 39 will contract out of engagement withthe wall of the casing 126 to thus release the plug 21 from the casingso that it can be retrieved by the tubular casing 102 with theretrieving unit 132.

The check valve 89, as best seen in FIGURES 12 to 17, is of circularcross section and includes an intermediate section 167, end sections 168and 169, a section 170 as interposed between the sections 167 and 168,and a section 172 which is interposed between the sections 167 and 169.The section 167 has restricted threaded ends 172 and 173 whichthreadedly engage in internally threaded inner end flanges 174 and 175of the sections 170 and 171, respectively. The sections 170 and 171 havechambers 174 and 175, respectively, which extend from their remote endsto the portions 172 and 173, respectively, and which chambers areconnected with one another by a plurality of passages 176 which extendlengthwise through intermediate section 167.

The bottom section 169 has a threaded nipple 177 which threadedlyengages in the upper end of the pipe 90 and which has a bore 178 whichextends to the outer end of said nipple which is flared at the inner endof the section 169 to provide a valve seat 179 for a ball valve 180. Theinner end of the section 169, which abuts the outer end of the section171, is recessed, as seen at 181, to accommodate the peripheral portionofa diaphragm 182 which is preferably formed of rubber and which spansthe valve seat 179 and has its center bearing. against and normallyretaining valve 180 in a closed position. Screws 182 which extendlengthwise through the end section 169 around the nipple 177 threadedlyengage in sockets 183 of the section 171 for clamping the peripheralportion of the diaphragm 182 between the sections 169 and 171 and forsecuring said sections together.

The intermediate section 167 has an axial bore 184 opening in to thechamber 175 and which contains a plunger-like spring abutment 185 havingan O-ring 186 disposed in an annular groove 187 thereof for sealing thebore 184. A compression spring 188 has one end seating in a socket 189which opens outwardly of the outer end of said abutment 185 and anopposite end seating in a cup 190 which is disposed in the chamber 175and which rests centrally on the diaphragm 182. The diaphragm 182 has aseries of small apertures 191 between the cup 190 and the part therewhich is clamped in the recess 181, as seen in FIGURES l3 and 17.

The restricted inner end of the bore 184 intersects with the inner endof a radial bore 192 of the section 176 which is threaded to receive anadjusting screw 193 having a conical inner end 194 which engages afrusto-conical inner end 195 of the abutment 185. Accordingly, when thescrew 193 is advanced inwardly, the surface 194 by camming engagementwith the surface 195 will displace the abutment 185 outwardly ordownwardly of the bore 184 for increasing the pressure of the spring188.

As seen in FIGURE 12, the exterior of the section 167 has a dished ringportion 196 surrounding the bore 192 and containing circumferentiallyspaced substantially hemispherical indentations 197 which are preferablydesigned by indicia 198 representing pressure in pounds. A spring arm199 extends transversely from the adjustment screw 193 and has aninturned rounded terminal 200, seen in FIGURE 13, disposed to yieldablyseat in any one of the indentations 197. Thus, it will be seen that thespring element 199 will latch the screw 193 against rotation indifferent adjusted positions, and when forcibly turned its end 200 willride into and out of engagement with the depressions 197.

An axial bore 201 opens through the outer end of the other end section168 and has an inner end communicating with an innerhemispherical-shaped recess 202 which opens through the inner side ofthe section 168. The section 168 9 at its inner side has an annularrecess 203 to accommodate the peripheral portion of an elastic rubberdiaphragm 204 which is secured therein by the screws 205 which extendinwardly through the section 168, through the peripheral portion of thediaphragm 204, and which are anchored in threaded sockets 206 of thesection 170.

The other end of the section 167 has a bore 184' opening into thechamber 174 and containing abutment 185'. A threaded radial bore 192contains an adjustment screw 193' which contacts the plunger 185. Theparts 184' and 185' correspond with the parts 184 and 185, respectively,and the parts 192 and 193 correspond with the parts 192 and 193,respectively, except that the parts 192' and 193 are oppositely threadedfrom the parts 192 and 193. The screw 193' is locked in diflerentadjusted positions by a spring 199' in the same manner as the screw 193.

One end of a spring 207 seats in the abutment 185' and extends therefrominto the chamber 174 and has its opposite end bearing against a ball 208which is also disposed in said chamber between the spring 207 and thecenter of the diaphragm 204. The diaphragm 204 has a ring of apertures209 spaced from the center thereof, as seen in FIGURES 13 and 14. Asseen in FIGURE 13, the spring 207 is heavier and stronger than thespring 188, and the diaphargm 204 is thicker and less elastic than thediaphragm 182.

The combined capacity of the apertures 191 and the combined capacity ofthe bores 176 is each greater than the combined capacity of theapertures 209. Assuming now that the lowering unit 22 is being extractedfrom the plug 21, as previously described, and until said unit clearsthe plug substantially no pressure will exist in the chamber 82, and theparts of the valve 89 will be disposed as seen in FIGURE 13. As thelowering unit clears the plug, hydrostatic and circulating fluids willfill the chamber 82 through the tube 81 to create a high pressuretherein. A part of this fluid will pass outwardly through the pipe 90and bore 178 to unseat the valve 180 so that the fluid can flow throughthe apertures 191. The pressure of the fluid against the under side ofthe diaphragm 182 will distend said diaphragm into the chamber 175 andcompress the spring 188.

The fluid will flow from the chamber 75 through the passages 176 to fillthe chamber 174 and some of this fluid will escape through the apertures209 and the bore 201 from the check valve. However, due to the lessercapacity of the apertures 209, the pressure will build up in the chamber174 which will act with the spring 207 for forcing the diaphragm 204outwardly until it reaches a fully distended position, as seen in dottedlines of FIG- URE 13, against the surface of the cavity 202. The ball208 will then be lining or filling the substantially hemi sphericalcentral portion of the diaphragm 204 so that the apertures 209 will besealed by their engagement against said cavity surface and to someextent by being engaged by the ball 208, to thus shut off the flow fromthe check valve 89. It will thus be seen that the check valve will closein response to a high pressure in the chamber 82.

Thereafter, when the retrieving unit is applied and the pressure in thechamber 82 is partially dissipated by opening of the valve 152, aspreviously described, this diminishing of pressure in the chamber 82will cause a reduction of pressure in the chambers 175 and 174 so thatthe diaphragm 204 can move out of contact with the hemispherical surfaceof the cavity 202 to expose the ape-rtures 209 to allow escape of thefluid from the chamber 174. As the pressure of said chamber diminishesthe diaphragm 204 will gradually return to its full line position ofFIGURE 13. Reduced pressure in the chamber 82 will also permit thespring 188 and diaphragm 182 to close or partially close the ball valve180, when the pressure in the chamber 175 is not much greater than thepressure in the chamber 82. However, as the pressure diminishes in thechamber 174 it will equalize with the chamber 175, and when thispressure has become sufiiciently more than the pressure in the chamber82, the valve will again open to allow further escape of the fluid fromthe chamber 82. However, this fluid will be at a relatively low pressureincapable of returning the diaphragm 204 to its dotted line position ofFIGURE 13, so that the valve 89 will remain open to permit escape of thefluid at a low pressure. The tube 84 contains a drainage port 210normally sealed by a threaded plug 211 which can be removed for drainingthe chamber 88 after the plug 21 has been retrieved.

Various modifications and changes are contemplated and may obviously beresorted to without departing from the function or scope of theinvention, as hereinafter defined by the appended claims.

I claim as my invention:

1. A device for sealing a well casing bore comprising a bridging plugincluding an elongated plug body, said body having an expansible lowerportion, a normally sealed chamber formed partially by said lowerportion, elastic sealing rings surrounding a part of said expansiblelower portion, a sealed container containing an expansible gas, apiercing member slidably mounted above said container; a lowering unithaving a lower part fitting slidably and detachably into an upper partof said plug body and by which the plug body is adapted to be loweredinto a well casing, latch means forming a part of said lowering unit bywhich said lower part is releasably latched in the plug body, a plungerslidably disposed in the .lower part of said lowering unit, meansforcibly driving said plunger downwardly from the lower part of saidlowering unit through a part of said plug for engaging and driving thepiercing member downwardly for rupturing said container to release thegas therefrom to pressurize and expand said lower portion for expandingsaid sealing rings into sealing engagement with the Well casing, andsaid plunger including a part engaging said latch means to effectunlatching thereof when the plunger is driven downwardly to permit saidlowering unit to be retrieved from the plug after the plunger hasactuated the piercing member a first housing connected to and extendingupwardly from a part of the expansible lower portion and defining anupper part of said expansible chamber, a second housing connected to andextending upwardly from the first housing and defining an upper chamber,a passage connecting said chambers and including a valve seat, an innertube extending upwardly from said upper housing and communicating withthe upper end of said upper chamber, an outer tube connected to a partof said expansible chamber and extending upwardly therefrom andsurrounding said housings and the inner tube, a plug sealing the upperend of the outer tube to the inner tube and combining with said tubes todefine a relief chamber, a valve connected to an upper end of saidpiercing member and disposed in said first housing, a spring urging saidvalve upwardly into seating engagement with said valve seat for closingthe passage between the upper chamber and said normally sealed chamberand for normally retaining said piercing member in a retracted positionout of engagement with said container; a retrieving unit adapted to belowered into the well casing including a hammer defining a lower leadingend thereof receivable into the plug through said inner tube for passagedownwardly through said inner tube and said upper chamber to engage andunseat said valve and for sealing the upper end of the passageconnecting the upper chamber and said sealed chamber, said lower housinghaving ports extending outwardly from the valve seat and opening intothe relief chamber for escape of the gas from the sealed chamber topermit the expansible lower portion and said sealing rings to retract,and spring urged latch members carried by said hammer for latching thehammer to the upper housing with the hammer disposed to seal the upperend of said passage to permit the plug to be retrieved from the wellcasing with said retrieving unit.

2. A device as in claim 1, normally closed valve means forming a part ofsaid plug and actuated by said retrieving unit entering said inner tubefor opening a passage between the lower portion of the inner tube andthe relief chamber to permit escape of hydrostatic and circulatingfluids from said inner tube and upper chamber into said relief chamberafter the upper end of the inner tube is sealed by the retrieving unit.

3. A device as in claim 2, a check valve forming a part of said plugdischarging into said relief chamber and communicating with said upperchamber, said check valve opening in response to a low pressure andclosing in response to a high pressure whereby said check valve willopen after the retrieving unit has entered said inner tube and has moveddownwardly therethrough to seal said relief valve for dissipating thefluid remaining in said upper chamber into said relief chamber.

4. A device for sealing a well casing bore comprising an alongated plughaving a norm-ally sealed chamber defining a lower part thereof and arelief chamber defining an upper :part of the plug, said plug having anexpansible portion constituting a lower part of said sealed chamber,elastic sealing rings engaging around and supported by said expansibleportion, a sealed container disposed in said sealed chamber andcontaining an expansible gas, an upper chamber connected to and risingfrom said sealed chamber, a tube connected to and extending upwardlyfrom said upper chamber and opening through an upper end of the plug; alowering unit including a lower part insertable through said tube intosaid upper chamher, latch means carried by said lower part for releas-30 ably latching the lowering unit to the plug whereby the plug isadapted to be lowered into the well casing by the lowering unit,explosive means carried by said lowering unit and operable to producepuncturing of said sealed container to release the gas therefrom topressurize said sealed chamber for expanding the expansible lowerportion to cause the sealing rings to assume sealing engagement with thewell casing and to effect release of said latch means to permit thelowering unit to be retrieved from the plug.

5. A device as in claim 4, a passage connecting said sealed chamber andrelief chamber, and a valve normally closing said passage; a retrievingunit adapted to be lowered into the well casing including a lowerportion receivable through said tube and upper chamber for no seatingthe valve for depressurizing the sealed chamber to release the plug fromthe well casing, and latch means carried by said lower part of theretrieving unit for latching the retrieving unit to the plug forretaining said valve in an open position and to permit the plug to beretrieved from the well casing with the retrieving unit.

References Cited UNITED STATES PATENTS 2,194,331 3/1940 Strorn 166-1872,326,404 8/ 1943 Spangler "166-63 2,784,790 3/1957 Boer et al. 166-632,966,946 1/1961 McCulloch et al. 166l87 3,029,872 4/1962 Hanes 166-63CHARLES E. OCONNELL, Primary Examiner.

I. A. LEPPINK, Assistant Examiner.

4. A DEVICE FOR SEALING A WELL CASING BORE COMPRISING AN ELONGATED PLUGHAVING A NORMALLY SEALED CHAMBER DEFINING A LOWER PART THEREOF AND ARELIEF CHAMBER DEFINING AN UPPER PART OF THE PLUG, SAID PLUG HAVING ANEXPANSIBLE PORTION CONSTITUTING A LOWER PART OF SAID SEALED CHAMBER,ELASTIC SEALING RINGS ENGAGING AROUND AND SUPPORTED BY SAID EXPANSIBLEPORTION, A SEALED CONTAINER DISPOSED IN SAID SEALED CHAMBER ANDCONTAINING AN EXPANSIBLE GAS, AN UPPER CHAMBER CONNECTED TO AND RISINGFROM SAID SEALED CHAMBER, A TUBE CONNECTED TO AND EXTENDING UPWARDLYFROM SAID UPPER CHAMBER AND OPENING THROUGH AN UPPER END OF THE PLUG; ALOWERING UNIT INCLUDING A LOWER PART INSERTABLE THROUGH SAID TUBE INTOSAID UPPER CHAMBER, LATCH MEANS CARRIED BY SAID LOWER PART FORRELEASABLY LATCHING THE LOWERING UNIT TO THE PLUG WHEREBY THE PLUG ISADAPTED TO BE LOWERED INTO THE WELL CASING BY THE LOWERING UNIT,EXPLOSIVE MEANS CARRIED BY SAID LOWERING UNTI AND OPERABLE TO PRODUCEPUNCTURING OF SAID SEALED CONTAINER TO RELEASE THE GAS THEREFROM THEPRESSURIZE SAID SEALED CHAMBER FOR EXPANDING THE EXPANSIBLE LOWERPORTION TO CAUSE THE SEALING RINGS TO ASSUME SEALING ENGAGEMENT WITH THEWELL CASING AND TO EFFECT RELEASE OF SAID LATCH MEANS TO PERMIT THELOWERING UNIT TO BE RETRIEVED FROM THE PLUG.